This is sort of tangential to coding, but programmers often do \"view source\" on their own pages and on others\' pages. I learned that when you do the normal View Source in
This solution was ok in 2012, but no longer nowadays.
Type "about:config" in the address bar.
In the filter box, type : "browser.cache"
"browser.cache.disk.enable" and "browser.cache.memory.enable" must be set to TRUE.
Done ! All credit to @MatrixFrog